Safety device for elevators



Nov. 18, 1924. I W. EDWARDS SAFETY DEVICE FOR ELEVATORS Filed July 5, 1922 /z.3 I 56' 31 17 as 6 61.42

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Patented Nov. 1%, i924.

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WILLIAM EDWARDS, OF WEST ROXBUBY, MASSACHUSETTS.

SAFETY DEVICE Application filed July 3,

To all whom it may concern:

Be it known that I, VVILLIAM EDWARDS, a subject of the United Kingdom of Great Britain and Ireland, residing at West Role bury, in the county of Suffolk and State of Massachusetts, have invented a new and useful Improvement in Safety Devices for Elevators, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to a safety device for elevators to prevent the dropping thereof in case the hoisting cable slackens or breaks, and is designed with special reference to low speed elevators.

The main object of the invention is the provision of a safety device of the character described, which is simple in construction and positive and efficient in its operation.

Another object is the provision of a device so constructed that after it has been operated, it can not be returned to an in operative position until the hoisting cable has been restored to normal condition and the elevator raised.

Other objects of the invention will be more specifically set forth and described hereinafter.

In the accompanying drawings illustrating the preferred embodiment of my inven tion, Fig. 1 is a front elevation of a freight elevator of ordinary construction, having a safety device constructed and operated in accordance with my thereto; Fig. 2 is a cross-sectional view on an enlarged scale on line 2-2 in Fig. 1, looking from left to right; and 3 is a view on an enlarged scale on line 3-3 in Fig. 1, looking from left to right, portions being broken away to show the cams.

Referring to Fig. 1 of the drawings, there is shown a freight elevator of ordinary construction comprising a floor 5 and a crosshead 6 connected together by uprights 7 at the sides, reinforced by rods 8 extending obliquely from the floor edges to the crosshead and secured to the latter by bolts 9. The floor is supported by a suitable frame work made up of side beams, each made up of two angle iron pieces 10 secured together by bolts 11 and nuts 12, which side beams are connected together by a cross-beam 13.

The elevator is raised and lowered by two cables 14, each secured to a yoke 15, and the two yokes are connected by pins 16, one to invention applied 1o FOB ELEVATORS.

1922. Serial No. 572,456.

each end of an evener bar 17, which in turn is centrally and pivotally connected to a drawbar 18 which passes loosely through the cross-head 6 and is, on its lower end, provided with a head 19 to prevent withdrawal. Plates 20 may be arranged on the top and bottom surfaces of the cross-head 6 to prevent wear. On the. sides of the elevator at convenient points, suitable U-shaped guides 21 are provided for engaging vertical guide rails .13 carried by vertical supports 24. All of the foregoing construction is old and well-known, and is shown merely to il1us-' trate the application of my invention witl1- out intending to limit that application to any particular form of elevator.

The novel features of my invention reside in a safety device comprising means adapted for gripping the guide rail to stop the elevator, said means being normally out of operation by gravity, and means controlled by the hoisting cable for throwing the gripping means into operation whenever the cable slackens Or breaks.

Any suitable form of gripping means may be provided, and one such form is shown in the drawings, comprising one or more pairs of cams 30 (Fig. 3), eccentrically mounted adjacent the guide rail 23. Preferably two pairs are employed, one for each of the guide rails, each pair being so arranged that the guide rail is gripped between the two cams. The corresponding cams of the two airs may be secured on rods 31 by keys 33, so that they may be operated in unison, the rods being loosely mounted in the side angle irons 10. Each cam is provided with a toothed segment 32 of gradually increasing radius, and in such close proximity to the guide rail that, when the cam is turned upwardly, the toothed segment bites into the guide rail to an increasing extent, Stops 35, fastened to an angle plate 10, may be provided to limit the upward movement of the earns 30. For operating the cams, each cam of the pair on the right, referring to Fig. 1, is fastened by a pin 36 located near' the toothed segment to a rod 38 extending upwardly along the side of the elevator, the upper end of the rod being threaded at 39 and provided with anut 40 thereon. A lever passing loosely through the cross-head 6, and the short arm of the lever is provided at its end with an opening adapted to re '42 is mounted eecentrically on a pin 43,

ceive loosely one of the rods 38. @n the re- 1 i verse side ot the eross-head, a short lever I corresponding: in length to the short arm o. the lever 42, is fastened on the pin l3, an: the end of the lever n is provided with a similar opening to receive the othe' ot the two rods 38. The movement of the lever '9 on its fulcrum l5 raises the two rods 88 or permits them to drop, and therehy rotate: the cams into gripping position or away from gripping position, as the case may be. The long arm of the lever 42 should be of sutlicient weight and length to norn'ially raise the two rods 38 the cams into i ping engagement with guide where two pairs of cams emp. a operate the other pair or cams likewise.

It will be observed that the normal position of the lever l. .i a lowermost 13031! H the cams into gdppino' and in order breaks to bring about tl.

the long arm. of the ever 51 most position so long a. the .3 ta for releasing it when the cable slaelzens oi breaks. the means is shown in t. ings, and comprises an L-shaped la pivotally mounted on a pin 5i ti bracket secured by oolts 3o to h plate 20. The rear end (it nected by a pin to a link a pin 56 to the evener bar being of such proportions cable is taut and the evener bar is held up. the latch is in the position shown in Fig. therehi locking); the lever in position v. its long arm uppermost. retaining band 60, secured by bolts and (3: to the bottom plate and the bracket 59. rcspectiwly. may be provided or preventing: any late.. l n'iovei'nent of the lever 42.

In order to secure a quick releas oi? the lever 42 from the latch who l ing cable either slackens or 7 any suitable means be provided tor accelerating the moven'rent ot the drawbar 16% downwardly in relation to the cross-head (l. and one such means is shown in the draw 2: consist" wider u when the i the lower and 0:. to an eye bolt 5" and the upper nected to ill no]. the pin The sprin sion' at all times. imme dropping of the eve.

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1d, thereby im -iv r 42 and causing the cams guide rails before the car 1; headway in its drop, c release of the level 4;? by the latch 50 may The operation of my safety device e2;- tremel simple and 18 as follows.

Normally the various parts are in the positions shown in the drawings, the lever as being held in its inoperative position by the latch 50, and the cams 30 being in outward engagement with the guide rails and held in a lowermost position by the force oi gravity. While the cams being eccentrically mounted tend naturally to assume the po sition shown in Fig. 3, the wei 'ht of the rods 38 insures the retention oi the cams in such position until the safety device is operated. After the lever has been locked in position by the latch 50, it can not be released, so long as the hoisting cable remains taut, without lifting the entire weight of the car in order to drop the evener bar in relation to the cross-head.

It for any reason the hoisting cable. 14: break or become slack, the drawbar 1.5, which is loosely mounted in the cross-head. 6, immediately drops through the force oi? gravity, thereby throwing out the nose oi. the latch 50 and releasing the lever 4-2. The long arm of the lever then drops, and the short arm and arm d4 move upwardly, en gaging the nuts an on the rods 38, raising the roos, and thereby turning the cams 30 into engagement with the guide rail or guide rails, as the case may be. The natural dropping ot the elevator car when the hoisting cable slackens or breaks will cause the cams 30 to continue their turning movement until they engage the stops 85, the cams as they turn biting further into the guide rails, generally made of wood or similar substance, whereby the car is stopped.

in order to release the car from this position assuming that the cable is returned to a tauteondition or repaired in case of brea age, the lever 42 must be returned int en gement with the latch 5.0 after which the car is moved upwardly whiclantennae ically turns the came back into normal. inoperative position. It. however. there is any question about the strength of the cable after the car has been stopped, the lever may be allowed to remain unlatched and he elevator car moved upwardly, in which case the cams will disengage from the guide rails and drag along the same, ready at any moment, when the hoisting cable slackens or breaks, to again engage the guide rail and stop the car in its downward. movement.

It will be observed that my safety device is of extreme simplicity, and is positive in its action at all times.

By providing means for drawing the drawbar downwardly in relation to the cross-head of the elevator in order to re.- lease the latch when the strain on the hoisting cable permits, I take care of all contingencies. For example: cases have been known where the drum upon which the hoisting cable is wound has been suddenly released, owing to the fact that the operating worm gear has been stripped due to wear, in which case the elevator has simply dropped rapidly without slackening the cable sufiiciently to throw the safety device into operation. In my device, however, such a contingency would be taken care of by the spring connecting the cross-head with the pin in the evener bar, thereby drawing the two members together and releasing the latch independly of any slackening of the hoisting cable. The spring in this instance is sufficiently strong to bring about this action, if the hoisting drum is released, so that the hoisting cable is played out without restriction.

Other advantages of my construction are that the parts are open to inspection at all times, thereby making it possible to detect any defects which may be due to wear or tear, and that the device may be tested without the use of a knockout stick. In many States the laws require an annual inspection and testing of elevators and safety devices thereon. In elevators of this class it is usually customary, in testing the safety device, to have a man go under the elevator, insert a knockout stick upon which the elevator is lowered and the hoisting cable run out until there are a number of feet of slack cable, when the knockout stick is pushed out and the elevator allowed to drop. This operation involves more or less danger to the man under the car, for the reasons that, if the stick is not sufficiently strong to support the elevator or slips away, the elevator is liable to drop and injure the man underneath. \Vith my device the presence of a man under the elevator is entirely unnecessary, because a barrel, box, or any similar article, may be placed under the elevator which is then lowered onto the box or barrel sufficiently to slacken the cable to release the latch, after which the elevator may be raised,

dragging the cams on the guide rail as heretofore explained, and then lowering to see if the cams catch and hold the car. Such a test demonstrates fully the operation of the safety device without endangering any lives or exposing anyone to in ury.

It is to be understood that my invention is not to be restricted to the particular embodiment herein shown and described, since it may be exemplified in various other forms of construction, and I desire to claim it broadly except where specifically limited in the following claims.

What I claim is: 1. The combination with an elevator car of a pair of normally inoperative cams for engaging the guide rail to stop the car, a

grz-tvity-operated lever for throwing said cams into operation, and a latch for holding said gravity-operated lever in a raised, inoperative position; said latch being arranged to release said gravity-operated lever whenever the hoisting cable becomes slack or breaks.

2. The combination with an elevator car of a pair of normally inoperative cams for engaging the guide rail to stop the car, a gravity-operated lever for throwing said cams into operation, and a latch for locking said gravity-operated lever in a raised position; said latch being so arranged that the slackening of the hoisting cable releases said gravity-operated lever.

3. The combination with an elevator car of normally inoperative means for engaging the guide rail to stop the car, a gravityoperated lever for throwing said engaging means into operation, and a latch for looking said gravity-operated lever in a raised position; said latch being so arranged that the slackening of the hoisting cable releases said gravity-operated lever.

4. The combination with an elevator car of a pair of cams for engaging the guide rail to stop the car, said cams being held normally in an inoperative position by gravity, a lever fulcrumed eccentrically on the cross-head of the elevator, the short arm of said lever being connected to said cams, means for holding the long arm of said lever in a. raised position, and means for automatically releasing said holding means whenever the hoisting cable slackens or breaks.

5. The combination with an elevator car of a pair of cams for engaging the uide rail to stop the car, said cams being held normally in an inoperative position by gravity, a lever fulcrumed eccentrically on the crosshead of the elevator, the short arm. of said lever being connected to said cams and the long arm of said lever being of suflicient weight to raise said cams into operative position, and a latch for holding said long arm of said lever in a raised position; said latch being automatically released whenever the hoisting cable slackens or breaks.

6. The combination with an elevator car of means for engaging the guide rail to stop the car, a lever fulcrumed eccentrically on said car, the short arm of said lever being connected to said means and the longarm being of sufficient weight to raise said short arm to throw said engaging means into operation, and a latch for holding said.

long arm of saidlever in a raised position; said latch being so arranged thatsaid lever is released therefrom Whenever the hoisting cable slackens or breaks.

"7. The combination with an elevator car ofra pair of normally inoperative cams for engaging the guide rail to stop the car, a lever fulcrumed eecentrically on said ear, the short arm of said lever being connected m to said cams and the long arm being of suiiicient Weight when released to raise said short arm to throw said cams into opera tion and a latch for holdingsaid long arm of said lever in a raised position; said latch being so arranged that vsaid lever is 15 released. therefrom Whenever the hoisting cable slackens or breaks.

In Witness whereof, I hereunto set my hand this thirtieth day of June, 1922.

WYILLIAM EDWARDS. 

